A box producing apparatus line for producing corrugated board sheet boxes from corrugated board sheets is provided with a paper supply section, a flexographic printing section, a slotting section for forming scorer lines, flaps, and joints, a perforating section, a folding section, and a joint bonding section, in this order, from the upstream.
Among them, the flexographic printing section performs printing on corrugated board sheets with flexographic inks using a flexographic printing machine.
As used herein, “flexographic printing” is one type of letter press printing techniques. Flexographic printing is a printing technique using printing blocks, made from rubber or synthetics resins, and liquid inks (water-soluble inks and UV inks), and has been employed for surface printing on corrugated board sheets, films, and textiles. Recently, improvements in the laser engraving and printing techniques enable more-precise printing, and new demands for the flexographic printing is being created.
Patent Reference 1 (Japanese Laid-Open Patent Application H10-296961) discloses a procedure for changing inks in a flexographic printing machine. Hereinafter, a flexographic printing machine and a procedure for changing inks in this flexographic printing machine, disclosed in Patent Reference 1, will be described with reference to FIGS. 11 and 12.
In FIGS. 11 and 12, a flexographic printing machine 100 includes an ink supply device 102, an anilox roll 104, a printing die 106, a printing cylinder 108, and an impression cylinder (receiving roll) 110, for printing on a corrugated board sheet “c”.
The printing die 106 is wound about the outer peripheral face of the printing cylinder 108, and a flexographic ink (hereinafter, simply referred to as an ink) “f” is supplied from the ink supply device 102 to the outer peripheral face of the anilox roll 104. The anilox roll 104 rotates while contacting the printing die 106 to transfer the ink “f” to the surface of the printing die 106. The impression cylinder 110 is provided under the printing cylinder 108 so as to face the printing cylinder 108. The corrugated board sheet “c” is inserted between the printing cylinder 108 and the impression cylinder 110 by means of rotations of the printing cylinder 108 and the impression cylinder 110, and the printing die 106 prints on the corrugated board sheet “c”.
The ink supply device 102 is provided with an ink chamber 112 which is enclosed with a chamber frame 114 that defines the rear wall and the left and right walls, a seal blade 116 provided at the upper end of the chamber frame 114, a doctor blade 118 provided at the lower end of the chamber frame 114, and the anilox roll 104 that rotates while contacting the blades 116 and 118. The ink chamber 112 is formed along the long axis direction of the anilox roll 104 such that an ink “f” stored in the ink chamber 112 contacts the outer peripheral face of the anilox roll 104.
Multiple (four, in FIG. 11) air supply ports 120 are provided along the longitudinal direction of the chamber frame 114 at the top of the chamber frame 114. An air supply branch pipe 124 branched from an air supply pipe 122 is connected to each air supply port 120. In the air supply pipe 122, a solenoid valve 126 is interposed, and a compressed air supply device (not shown), such as a compressor, for supplying compressed air “a”, is connected.
Furthermore, an ink supply port 128 is formed at the bottom of the center with respect to the longitudinal direction of the chamber frame 114, and an ink supply pipe 130 is connected to the ink supply port 128. An ink pump 132 and a solenoid valve 134 are interposed in the ink supply pipe 130, and the ink supply pipe 130 is connected to an ink container 136.
An ink recovery system for recovering the ink “f” in the ink chamber 112 to the ink container 136 is constructed from ink recovery pipes 142 connected to ink recovery ports 138 formed at the bottom ends of the chamber frame 114; excessive ink recovery pipes 144 connected to the excessive ink recovery ports 140 (for maintaining constant ink fluid level) formed at the upper ends of the chamber frame 114; solenoid valves 146 interposed in the ink recovery pipes 142; and an ink recovery pipe 148 connecting between the ink recovery pipes 142 and the excessive ink recovery pipes 144, and the ink container 136.
A cleaning water supply pipe 152 is connected to the ink supply pipe 130 between the solenoid valve 134 and the ink pump 132, via a solenoid valve 150.
In this configuration, during normal printing operations, the ink pump 132 is operated with the solenoid valve 150 being closed and the solenoid valve 134 being opened, to supply the ink “f” from the ink container 136 through the ink supply port 128 into the ink chamber 112. At this time, the solenoid valves 146 are closed, and the ink “f” is maintained to a certain ink fluid level in the ink chamber 112, since any excessive ink overflows from the excessive ink recovery ports 140.
For changing inks, the ink pump 132 is operated in the reverse direction to recover the ink “f” in the ink chamber 112 from the ink supply port 128, as well as opening the solenoid valves 146. Subsequently, the solenoid valve 126 is opened to supply the compressed air “a” from the air supply pipe 122 into the ink chamber 112, thereby pressurizing the ink chamber 112. As a result, the ink “f” in the ink chamber 112 is forcefully collected from the ink supply pipe 130 and the ink recovery pipe 148 to the ink container 136. After a predetermined time duration, the solenoid valve 126 is closed to stop the supply of the compressed air “a”.
For ink cleaning, the ink container 136 is replaced with a waste fluid pit (not shown), and the solenoid valves 134 and 146 are closed. Subsequently, the solenoid valve 150 is opened, as well as operating the ink pump 132 in the forward direction, to supply cleaning water “w” from the cleaning water supply pipe 152. The cleaning water “w” is supplied into the ink chamber 112 via the same path during the circulation of the ink “f”, and the ink chamber 112 is filled with the cleaning water “w”. The cleaning water “w” is then collected from the excessive ink recovery ports 140 to the waste fluid pit, through the ink recovery pipe 148. This operation is repeated for a predetermined time duration to clean inside the ink circulation path.
For collecting the cleaning water, the solenoid valve 150 is closed to stop the supply of the cleaning water “w”, and the solenoid valves 134 and 146 are opened. Subsequently, the ink pump 132 is operated in the reverse direction and the solenoid valve 126 is opened to supply the compressed air “a” from the air supply pipe 122 into the ink chamber 112. As a result, the cleaning water “w” in the ink chamber 112 is drained out of the ink chamber 112 from the ink supply port 128 and the ink recovery ports 138, under the pressure by the compressed air “a”, and is forcefully collected into the waste fluid pit.
Subsequently, the ink supply pipe 130 and the ink recovery pipe 148 are connected to an ink container 136 for a subsequent order. An subsequent order ink “f” is supplied to the ink chamber 112 through the ink supply pipe 130, for commencing printing of the subsequent order.